The invention relates to a method for the precise mounting of a MacPherson suspension strut.
The invention also relates to a device for the precise mounting of a MacPherson suspension strut making it possible, in particular, to implement the steps of the method according to the invention.
Document EP- 0 780 250 A2 describes the precise adjustment of a MacPherson suspension strut, using adjusting means on the strut and advantageously measuring the mechanical properties of the strut using an appropriate measurement bench.
A MacPherson suspension strut comprises a compressively preloaded coil spring.
Whereas contact is over at least three sectors when the spring is in the compressed state, the spring in the unconstrained state before compression is generally in contact with each upper or lower spring retainer at just one point.
This limited point contact is detrimental to the precision with which MacPherson suspension struts can be mounted.
In current mounting machines, attempts are made at improving the precision of the mounting by centering the spring by providing secondary contact on the outside of the turns, by precompressing the spring before it is mounted on the strut, or by using equivalent means.
However, the current solutions are not satisfactory and lead to imprecise spring centering, because this centering is sensitive to the spread on the mechanical properties of the springs.
The object of the invention is to overcome the drawbacks of the prior art by proposing a new technique for the precise mounting of MacPherson suspension struts, which is insensitive to the mechanical and geometric variations of the springs, and which is economical and easy to implement.
The subject of the invention is a method for mounting a MacPherson suspension strut, comprising the following steps:
a) introducing the constituent elements; of the strut under a mounting head which has at least one degree of freedom in tilting;
b) mating the upper end of the strut with a part of the mounting head;
c) compressing the spring by shifting the mounting head relative to an immobilizing means engaged with the body of the shock absorber;
d) mounting the strut with its preloaded spring when said part of the mounting head comes into abutment and when the shock absorber rod protrudes through the upper spring retainer.
According to other features of the invention:
the part of the mounting head has two degrees of freedom in tilting;
the part of the mounting head is mounted on the body of the mounting head by a universal joint;
the part of the mounting head is guided in sliding relative to the body of the mounting head.
Another subject of the invention is a device for the precise mounting of a MacPherson suspension strut, comprising a means of immobilizing a shock absorber connected to a mounting head which can be shifted one with respect to the other, characterized in that the mounting head has a part with at least a degree of freedom in tilting and capable of mating with an upper spring retainer of a strut, so as to allow the spring to be compressed without introducing parasitic loadings.
According to other features of the invention:
the device comprises at least one limit stop for stopping said part in a chosen predetermined orientation;
said part is mounted on the body of the mounting head via a universal joint;
said part is shaped as a plate to take an upper spring retainer with a central passage;
the mounting head has a second part of predetermined orientation capable of limiting the tilting movement of said part while the spring is being compressed;
the second part is shaped as a stop plate carrying at least one limit stop position stop.